Determination of differential code biases with multi-GNSS observations

Abstract

In order to better understand the differential code biases (DCBs) of Global Navigation Satellite System, the IGGDCB method is extended to estimate the intra- and inter-frequency biases of the Global Positioning System (GPS), GLONASS, BeiDou navigation satellite system (BDS), and Galileo based on observations collected by the Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS). In the approach of IGGDCB, the local ionospheric total electronic content is modeled with generalized triangular series (GTS) function rather than using a global ionosphere model or a priori ionospheric information. The DCB estimated by the IGGDCB method are compared with the DCB products from CODE (the Center for Orbit Determination in Europe), DLR (German Aerospace Center), and the broadcast timing group delay parameters for the years of 2013 and 2014. The results indicate that GPS and GLONASS intra-frequency biases obtained in this work show the same precision as those estimated by DLR (about 0.1 and 0.2~0.4 ns for the two constellations, respectively, relative to the products of CODE). The precision of the IGGDCB-based inter-frequency biases estimated over the 24-month is about 0.29 ns for GPS, 0.56 ns for GLONASS, 0.36 ns for BDS and 0.24 ns for Galileo. Here, the accuracy of GPS and GLONASS biases is assessed relative to the products of CODE, while that of BDS and Galileo is compared to the estimates of DLR. In addition, the monthly stability of IGGDCB-based DCBs are 0.11 (GPS), 0.18 (GLONASS), 0.17 (BDS) and 0.14 (Galileo) ns for the individual constellation, respectively.